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Generic name: ofatumumab
Dosage form: injection, for subcutaneous use
Drug classes: CD20 monoclonal antibodies, Selective immunosuppressants

Medically reviewed by Melisa Puckey, BPharm. Last updated on Oct 13, 2022.

What is Kesimpta?

Kesimpta (ofatumumab) is a FDA approved medicine used to slow the progression and risk of relapses for specific forms of relapsing multiple sclerosis (MS). It is a once a month injection given under the skin (subcutaneously) that you can self-administer in your own home.

Kesimpta is from the group of medicines called CD20 monoclonal antibodies that targets B-cell antigens. Sometimes they are called B-cell therapy or B-cell depletion therapy. Kesimpta works by binding to and decreasing B-cells. This medicine will not cure MS, but is used to slow its progression and reduce relapse rate.

How does Kesimpta work?

MS is a chronic, ongoing disease that causes damage to the brain, spinal cord and optic nerves. This causes nerve signals to be interrupted and results in symptoms of numbness, tingling, mood changes, memory problems, pain, fatigue, blindness and/or paralysis. It is thought that B-cells play a critical role in MS which causes the immune system to attack nerves. Kesimpta works by binding to and decreasing the B-cells, which may slow your immune system attacking your nerves. This may decrease inflammation and reduce MS symptoms, slow your disability progression and lower relapse rate.

What is Kesimpta used for?

Kesimpta is used in adults with specific types of relapsing forms of multiple sclerosis (MS) including:

  • clinically isolated syndrome (CIS)
  • relapsing-remitting MS (RRMS)
  • active secondary progressive disease (active SPMS)

Arzerra (ofatumumab) contains the same active ingredient to Kesimpta (ofatumumab) but they are NOT to be used interchangeably. They are used to treat different conditions and are given by a different route of administration.


Kesimpta can cause serious side effects, including:

  • Infections. Serious infections can happen during treatment with this medicine. If you have an active infection, your healthcare provider should delay your treatment until your infection is gone. Kesimpta taken before or after other medicines that weaken the immune system may increase your risk of getting infections.

Tell your healthcare provider right away if you have any infections or get any symptoms, including painful and frequent urination, nasal congestion, runny nose, sore throat, fever, chills, cough, or body aches.

  • Hepatitis B virus (HBV) reactivation. Before starting treatment, your healthcare provider will do blood tests to check for HBV. If you have ever had HBV infection, the HBV may become active again during or after treatment. Hepatitis B virus becoming active again (called reactivation) may cause serious liver problems, including liver failure or death. You should not receive this medicine if you have active hepatitis B liver disease. Your healthcare provider will monitor you for HBV infection during and after you stop using this medicine.

Tell your healthcare provider right away if you get worsening tiredness or yellowing of your skin or white part of your eyes during treatment.

  • Progressive Multifocal Leukoencephalopathy (PML). PML may happen with this medicine. PML is a rare, serious brain infection caused by a virus that may get worse over days or weeks. PML can result in death or severe disability. Tell your healthcare provider right away if you have any new or worsening neurologic signs or symptoms. These may include weakness on one side of your body, loss of coordination in arms and legs, vision problems, changes in thinking and memory which may lead to confusion and personality changes.
  • Weakened immune system. Kesimpta taken before or after other medicines that weaken the immune system could increase your risk of getting infections.

Who should not take Kesimpta?

Do not use this medicine if you:

  • have active hepatitis B virus infection.

Before using Kesimpta

Before using this medicine, tell your healthcare provider about all of your medical conditions, including if you:

  • have or think you have an infection including HBV or PML. See Important information.
  • have ever taken, currently take, or plan to take medicines that affect your immune system. These medicines could increase your risk of getting an infection.
  • have had a recent vaccination or are scheduled to receive any vaccinations.
    • You should receive any required ‘live’ or ‘live-attenuated’ vaccines at least 4 weeks before you start treatment. You should not receive ‘live’ or ‘live-attenuated’ vaccines while you are being treated with this medicine and until your healthcare provider tells you that your immune system is no longer weakened.
    • Whenever possible, you should receive any ‘non-live’ vaccines at least 2 weeks before you start treatment with Kesimpta.
    • Talk to your healthcare provider about vaccinations for your baby if you used Kesimpta during your pregnancy.
  • are pregnant, think that you might be pregnant, or plan to become pregnant. It is not known if this medicine will harm your unborn baby. Females who can become pregnant should use birth control (contraception) during treatment with this medicine and for 6 months after your last treatment. Talk with your healthcare provider about what birth control method is right for you during this time.
  • are breastfeeding or plan to breastfeed. It is not known if this medicine passes into your breast milk. Talk to your healthcare provider about the best way to feed your baby if you take this medicine.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

Know the medicines you take. Keep a list of them to show your healthcare provider and pharmacist when you get a new medicine.

How should I use Kesimpta?

See the detailed Instructions for Use that comes with Kesimpta for information about how to prepare and inject a dose of this medicine and how to properly throw away (dispose of) used pens or prefilled syringes.

  • Use Kesimpta exactly as your healthcare provider tells you to use it.
  • Kesimpta is given as an injection under your skin (subcutaneous injection), in your thigh or stomach-area (abdomen) by you or a caregiver. A caregiver may also give you an injection in your upper outer arm.
  • Your healthcare provider will show you how to prepare and inject this medicine the right way before you use it for the first time.
  • Do not inject into areas where the skin is tender, bruised, red, scaly or hard. Avoid areas with moles, scars or stretch marks.
  • The initial dosing is 20 mg of Kesimpta given by subcutaneous injection at Weeks 0, 1, and 2. There is no injection at Week 3. Starting at Week 4 and then every month, the recommended dose is 20 mg of Kesimpta administered by subcutaneous injection.
  • If you miss an injection at Week 0, 1, or 2, talk to your healthcare provider. If you miss a monthly injection, give it as soon as possible without waiting until the next scheduled dose. After that, use your injections a month apart.

Kesimpta side effects

Kesimpta may cause serious side effects, including:

See Important information

  • Injection-related reactions. Injection-related reactions is a common side effect of Kesimpta. Injecting this medicine can cause injection-related reactions that can happen within 24 hours (1 day) following the first injections and with later injections. Talk with your healthcare provider if you have any of these signs and symptoms:
    • at or near the injection site: redness of the skin, swelling, itching and pain or
    • that may happen when certain substances are released in your body: fever, headache, pain in the muscles, chills, and tiredness.
  • Low immunoglobulins. Kesimpta may cause a decrease in some types of antibodies. Your healthcare provider will do blood tests to check your blood immunoglobulin levels.

The most common Kesimpta side effects include:

  • upper respiratory tract infection, with symptoms such as sore throat and runny nose, and headache. See Important information
  • headache

These are not all the possible side effects of Kesimpta. Call your doctor for medical advice about side effects.

You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Kesimpta?

Tell your doctor about all your other medicines, especially drugs that weaken the immune system such as

  • cancer medicine
  • steroids
  • medicines to prevent organ transplant rejection.

This list is not complete. Other drugs may affect Kesimpta, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

How should I store Kesimpta?

  • Store this medicine in a refrigerator between 36°F to 46°F (2°C to 8°C).
  • Keep this medicine in the original carton until ready for use to protect from light.
  • Do not freeze.
  • Do not shake.

Keep Kesimpta and all medicines out of the reach of children.

General information about the safe and effective use of Kesimpta

Medicines are sometimes prescribed for purposes other than those listed in a Medication Guide. Do not use this medicine for a condition for which it was not prescribed. Do not give it to other people, even if they have the same symptoms that you have. It may harm them.You can ask your pharmacist or healthcare provider for information that is written for health professionals.

What are the ingredients in Kesimpta?

Active ingredient: ofatumumab
Inactive ingredients: Sensoready pen and prefilled syringe: arginine, disodium edetate, polysorbate 80, sodium acetate trihydrate, sodium chloride, and Water for Injection. Hydrochloric acid may be added.

Popular FAQ

In patients with relapsing forms of multiple sclerosis, Kesimpta (ofatumumab) is thought to be more effective than Ocrevus (ocrelizumab) in some ways, but no clinical trials have directly compared the two drugs

Ocrevus is the only one of the two drugs approved to treat primary progressive multiple sclerosis Continue reading

Arzerra (ofatumumab) is administered by an intravenous infusion. It is diluted into a sterile bag of 1000mL sodium chloride for intravenous infusion which is then hung up and the infusion administered into one of your veins via an intravenous line. How long the infusion takes depends on your stage of Chronic Lymphocytic Leukemia (CLL) and if you have had treatment before, but initially Arzerra is usually administered over about 6 hours. The time of the infusion may be shortened, depending on how well you tolerate Arzerra. Continue reading

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.